Comparative evaluation of sperm parameters in Italian (Apis mellifera ligustica) and Africanized (Apis mellifera) honeybee drones from the Caatinga biome

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Abstract
Bees are essential pollinators with species differing morphologically and physiologically. Understanding the variations in reproductive parameters between phenotypes is crucial. This study compares the sperm characteristics of Italian (Apis mellifera ligustica) and Africanized drones (Apis mellifera L.) raised in the Caatinga biome. Nine sexually mature Italian drones and sixteen Africanized drones from different colonies were used. Semen was collected using the endophallus eversion technique and diluted in saline solution (1:20). The parameters analyzed included: motility (optical microscopy), sperm viability (Hoechst 33342; propidium iodide), functional integrity of the plasma membrane (hypo-osmotic test), morphology and morphometry (Rose Bengal), and scanning electron microscopy. The results were expressed as mean ± standard error. Statistical analyses included the Shapiro-Wilk test to the normality of residuals and the Bartlett test to verify homoscedasticity. Comparisons between groups were performed using the Mann-Whitney and Student's t-tests (P < 0.05). Both phenotypes presented 90% sperm motility with viability of 82.4 ± 2.5% for Italians and 81.1 ± 2.4% for Africanized ones; the functional integrity of the plasma membrane was 93.4 ± 1.8% and 91.6 ± 1.5%, respectively. Regarding morphology, the percentage of normal sperm was 10.89 ± 1.66% for Italian and 12.06 ± 1.01% for Africanized, with the curled tail being the most predominant feature of sperm morphology. No statistically significant differences (P > 0.05) were observed for the above-mentioned parameters. Sperm head morphometry was significantly larger (P < 0.05) in Italian (10.04 ± 0.03 µm) compared to Africanized (9.33 ± 0.04 µm). Scanning electron microscopy analysis revealed no ultrastructural differences between phenotypes. In conclusion, there is a high degree of similarity in sperm parameters of both phenotypes under the same environmental conditions, indicating the feasibility of applying similar reproductive strategies.
Funding Information
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico (152230/2025-4)
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico (306409/2022-4)

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